Heretofore, the results of compaction work have been assessed by means of various methods of measuring the density of the surface, its coefficient of elasticity and the like.
One method that has proven particularly effective for this purpose uses a vibratory roller equipped with at least one vibrating drum. An evaluation is made of the signals received from transducers mounted on the roller as it passes over the ground for which the degree of compaction is to be measured and deviations from the pure sinusoidal form of the signals generated by the transducers constitute a measure of the degree of compaction of the ground. The signals from the transducers after certain processing actuate an indicating instrument mounted on the instrument panel of the roller and enable the operator to read the variations in the signals coming from the transducers directly thereby obtaining a visual indication of the degree of compaction of the ground.
Because the ground is as a rule particularly noncohesive and varying, the reading delivered by the indicating instrument is varying as well. On harder surfaces, the irregularity of drum motion increases because of the relatively long linear contact between the drum and the ground, which as a consequence of this condition increases the variation in the indicator reading. The operator experiences this variation as disturbing and in difficult circumstances it can impair the ability of the operator to read the indicating instrument and thus correctly judge the degree of compaction.